Introduction to Fastener Steel

Steel is the most basic material in fasteners. Although the application proportion of non-ferrous metals and composite materials is increasing year by year, the role of steel used in high-strength fasteners cannot be replaced. Various fasteners are usually made of cold-headed steel. In terms of variety classification, in addition to carbon steel, the steel used for fasteners also includes stainless steel, high-temperature alloy steel, aluminum-magnesium alloy, Monel alloy and so on. Among them, stainless steel and non-ferrous metals account for about 5% to 7% of the total consumables, except for cold heading wires. Cold heading steel wire rods and wire rods are generally low- and medium-carbon high-quality carbon structural steel and low-alloy steel. Low carbon cold heading steel is mainly used for cold heading nuts. The materials of bolts and screws are mainly medium carbon steel (ML35 and SWRCH35K), which can reach Grade 8 and above after quenching and tempering treatment.

Cold heading is formed by metal plastic at room temperature. Cold heading performance is one of the important properties of cold heading steel. Its performance is mainly reflected in its good cold formability; it must have as little resistance as possible and possibly high deformability for deformation. Because of the good cold forming performance of cold heading steel, cold drawing is used in the machining industry instead of hot-rolled material cutting machine processing. The advantage of this process is that it saves a lot of man-hours while reducing metal consumption by 10%-30%, which is in line with clean production. , The large-scale production of resource-saving enterprises, and the product size accuracy is high, the surface finish is good, and the production efficiency is high. It is the advanced machining technology that is promoted. Therefore, the use of cold heading technology to manufacture fasteners not only has high efficiency and good quality, but also saves materials and low cost.

Although the development of domestic cold-heading steel wire rod and wire rod started late, it has developed rapidly. Especially since the mid-1980s, high-speed wire rod production lines and wire rod continuous rolling production lines have been put into production. The production provides a guarantee on the equipment. At the end of 2005, the production capacity of cold heading wire rod reached 6 million tons per year (accounting for about 10-12% of the total wire rod amount). The steel mills of Baosteel, Maanshan Iron & Steel, Xing Steel, Xiangtan Iron and Steel, and Hangzhou Iron & Steel, which have established cooperative relations with the fastener industry, have formed an industry group for cold heading wire rods in my country. The product variety includes low-carbon, ultra-low-carbon, medium-carbon (quenched and tempered), low-alloy alloy steel and surface carburizing and hardening steel, with specifications ranging from 5.5 to 42mm, which almost cover all the needs of fastener steel. .

In recent years, with the rapid development of China's fastener industry, the demand for fastener steel has also increased significantly. Steel occupies almost 100% of the weight of fastener products. At the same time, considering the 15%-20% material loss in the production process, one ton of fasteners requires approximately 1.18-1.25 tons of steel, and the amount of steel consumed by fasteners is equivalent each year. considerable. According to relevant data, the national demand for fasteners in the cold heading steel market reached 3 million tons in 2003, and the demand increased to 4.5 million tons in 2005. In 2006, the national demand reached more than 5.5 million tons, and it is expected to increase to more than 5.5 million tons in 2007. 8 million tons.